The present invention relates generally to a nonwoven fabric, and specifically, to a nonwoven fabric having imparted therein a diaphanous bundled fiber pattern, whereby the nonwoven fabric exhibits an improved abrasive surface and high absorbency for use in cleaning, scrubbing, and wound debridement
Diaphanous materials routinely used in cleaning and medical applications include the use of xe2x80x9cgauzexe2x80x9d or xe2x80x9ccheese-clothxe2x80x9d like materials. These materials are typically manufactured by conventional textile fabric processes.
The production of conventional textile fabrics is known to be a complex, multi-step process. The production of fabrics from staple fibers begins with the carding process where the fibers are opened and aligned into a feedstock known as sliver. Several strands of sliver are then drawn multiple times on drawing frames to further align the fibers, blend, improve uniformity as well as reduce the diameter of the sliver. The drawn sliver is then fed into a roving frame to produce roving by further reducing its diameter as well as imparting a slight false twist. The roving is then fed into the spinning frame where it is spun into yarn. The yarns are next placed onto a winder where they are transferred into larger packages. The yarn is then ready to be used to create a fabric.
For a woven fabric, the yarns are designated for specific use as warp or fill yarns. The fill yarn packages (which run in the cross direction and are known as picks) are taken straight to the loom for weaving. The warp yarns (which run on in the machine direction and are known as ends) must be further processed. The packages of warp yarns are used to build a warp beam. Here the packages are placed onto a warper, which feeds multiple yarn ends onto the beam in a parallel array. The warp beam yarns are then run through a slasher where a water-soluble sizing is applied to the yarns to stiffen them and improve abrasion resistance during the remainder of the weaving or knitting process. The yarns are wound onto a loom beam as they exit the slasher, which is then mounted onto the back of the loom. Here the warp and fill yams are interwoven or knitted in a complex process to produce yardages of cloth.
The complexities inherent to woven textile processes in gauze or cheesecloth manufacture have been recognized as a critical limitation to efficient manufacture. The production of nonwoven fabrics from staple fibers is known to be more efficient than traditional textile processes as the fabrics are produced directly from the carding process. Nonwoven fabrics are suitable for use in a wide variety of applications where the efficiency with which the fabrics can be manufactured provides a significant economic advantage for these fabrics versus traditional textiles. Hydroentangled fabrics have been developed with improved properties that are a result of the entanglement of the fibers or filaments in the fabric providing improved fabric integrity. U.S. Pat. No. 3,485,706, to Evans, hereby incorporated by reference, discloses processes for effecting hydroentanglement of nonwoven fabrics. More recently, hydroentanglement techniques have been developed which impart images or patterns to the entangled fabric by effecting hydroentanglement on three-dimensional image transfer devices. Such three-dimensional image transfer devices are disclosed in U.S. Pat. No. 5,098,764, hereby incorporated by reference, with the use of such image transfer devices being desirable for providing a fabric with enhanced physical properties.
Prior art attempts to manufacture suitable diaphanous nonwoven fabrics for cleaning and medical applications have met with limited success. U.S. Pat. No. 4,555,430 to Mays, describes the use of staple length fibers in two different staple length populations and a thermoplastic binding component. U.S. Pat. No. 4,612,226 to Kennette et al., describes a wiping cloth having high abrasion resistance through the use of adhesive binder chemistry. U.S. Pat. Nos. 4,693,922 and 4,735,842, to Buyofsky et al., describe lightweight materials having a preponderance of thermoplastic staple fibers. The aforementioned U.S. Pat. No. 5,098,764, is directed to a nonwoven fabric whereby specific fibrous geometries are necessary for fabric performance. U.S. Pat. No. 5,648,141, to Butterworth et al., incorporated herein by reference, describes a debridement sponge manufactured from apertured nonwoven fabric.
An unmet need exists for a diaphanous nonwoven fabric, suitable for cleaning and medical applications, whereby a combination of fiber selection and performance attributes is obtained without the necessary use of binder or binding component.
In the present invention, a hydroentangled and three-dimensionally patterned fibrous material is formed from a fibrous matrix to produce a nonwoven fabric of pronounced open area and enhanced physical properties, including abrasive, and particularly wet abrasive, performance. A three-dimensional pattern utilized on the forming surface results in the nonwoven fabric having a diaphanous gauze-like or cheesecloth-like presentation.
A method of making a nonwoven material embodying the principles of the present invention contemplates the use of staple length fibers to facilitate economical fabric formation. Formation of the fibrous nonwoven fabric on a three-dimensional, image transfer device by hydroentangling imparts desired physical properties to the fabric such as the controlled placement of the fiber population relative to the desired three-dimensional pattern of the imaging device. This nonwoven fabric may be natural or colored.
A method of making a nonwoven fabric in accordance with the present invention includes providing a precursor web comprising staple length fibers. Fibers can comprise thermoplastic, thermoset, or natural fiber compositions. Preferred thermoplastic fiber composition include; polyester, polyolefin, polyamide, and the blends thereof. Natural fibers of particular interest are cotton fibers, in either virgin or recycled form.
Suitable mechanism of forming such precursor webs includes: carded fibrous batt, cross lapped fibrous batts, air-randomized fibrous batts, consolidated non-woven fabric, and combinations thereof. A preferable method of forming a suitable precursor web is through the pre-entanglement of staple fibers on a foraminous forming surface through the use of high-pressure water jets.
The present method further entails the provision of a three-dimensional, image transfer device having an array of three-dimensional surface elements thereon. The precursor web is positioned on the image transfer device, and hydroentangled to form the diaphanous nonwoven fabric.
The performance of the nonwoven fabric can be altered by varying the blend ratio of the thermoplastic fiber to the natural fiber used in the manufacture of the fabric. Sufficient absorbency, while maintaining durable wet abrasive performance, can be obtained by using no less than about 50% by weight natural fiber, the remainder of the weight-comprising polymer staple fibers. The nonwoven fabric can also comprise multiple layers of either blended fibrous components, or, preferably, the layering of one or more fibrous layers, which can be of either homogenous or heterogeneous composition.
The present invention further contemplates the addition of a physical performance modifying chemistries into or upon either one or more of the fibrous components or to the resulting nonwoven fabric.